Tutorial: Getting Started with Protege-Frames
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How do I create an ontology?
There is no one correct methodology for developing ontologies, nor is there a single correct result. Developing an ontology is usually an iterative process. You start with a rough first pass at the ontology. You then revise and refine the evolving ontology and fill in the details.

In practical terms, developing an ontology includes:
  1. defining classes in the ontology
  2. arranging the classes in a subclass-superclass hierarchy
  3. defining slots and describing allowed values for these slots
  4. filling in the values for slots for instances